Pillow

ABSTRACT

A pillow that changes its height during lying on the back and lying sideways, automatically and reliably according to sleeping posture of a user. No adjustment is necessary, and the height is stable. A biasing device provided in a hollow of the head placement member of a pillow is equipped with a link mechanism including a load supporting link, a rear end side of which being placed slidably on an upper end portion of a rear side link and a front end side thereof being connected rotatably to a front end side of an upper side link, and a tension spring for biasing the load supporting link to push the same upwards.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a pillow used for bedclothes, and more specifically to a pillow whose height during lying on the back and lying sideways changes automatically.

2. Description of the Related Art

As a posture of a person during sleep, the state where laying the standing upright state as it is to a lying on the back is most natural and is preferable. At this time, an occipital region of a head of a person which becomes the lowest position out of the head is at a position slightly higher than a back of the person. Therefore, in the pillow used as the bedclothes, it is preferable that the position of the occipital region of the head is made slightly higher than that of the back, when a person is sleeping on the back (hereinafter referred to as during lying on the back).

On the other hand, when a person rolls over during sleep to sleep sideways (hereinafter referred to as during lying sideways), the head is supported by a shoulder, so that the position of the head becomes higher than during lying on the back. Therefore, it is preferable that the pillow automatically changes its height depending on during lying on the back and lying sideways.

However, conventional ordinary pillows are produced while setting an intermediate height corresponding to a posture of lying on the back and a posture of lying sideways, assuming that the user sleeps while rolling over between the two lying postures. As a result, the pillows were too high during lying on the back and too low during lying sideways, and were not satisfactory. Further, pillows made of a soft low-resilience urethane form are available in the market, which provides sufficient lowness during lying on the back. However, they do not serve the purpose of the pillow during lying sideways because they are too low. Still further, pillows exclusive for lying sideways whose height is high using excess amount of short pipes or beads are available in the market. However, they are not suitable for use during lying on the back because they are too high, and may cause disorder to a neck of a person.

Therefore various pillows which automatically change its height according to the sleeping posture have been proposed. In such pillows, most of them identifies whether the sleeping posture is a posture of lying on the back or a posture of lying sideways, and changes the height of the pillow depending on the identified result. For example, Patent Documents 1 through 3 disclose burying a plurality of sensors for detecting pressure and area to a mattress or the like, identifies the sleeping posture by determining whether the portion contacting the mattress is a side portion or a back portion of a body depending on a contact area obtained from the detected result of each sensor, and changing the height of the pillow by adjusting an air amount inside a bag inside the pillow using an electric compressor and the like, or by elevating and lowering a link member using a motor, according to the sleeping posture.

However, in such pillows, when a body deviates from a predetermined position of the mattress by rolling over, the sleeping posture cannot be identified precisely, so that malfunction occurs. Further, they are not preferable because such pillow generates motoring sound and vibration, as well as requires electric source.

Therefore, there is proposed a pillow which changes its height automatically using the fact that load borne by the pillow differs between a posture of lying on the back disclosed a pillow equipped with a lower supporting plate, a head supporting plate provided approximately in parallel to the lower supporting plate for placing head thereon, a supporting plate supporting mechanism which is provided on the lower supporting plate to support the head supporting plate vertically movable while maintaining the approximately parallel state, and a cushion member placed on the head supporting plate, wherein the supporting plate supporting mechanism has a first supporting member and a second supporting member the lower ends of which being connected rotatably to the lower supporting plate and the upper ends of which being connected rotatably to the head supporting plate, and that are tilted and extended from the lower supporting plate to the head supporting plate in parallel to each other, and a biasing element such as coil spring for biasing the first supporting member and the second supporting member via the head supporting member against the load for bringing them down to the tilted direction.

When a user takes a posture of lying on the back with the head placed on the cushion member of the pillow, the first and the second supporting members fall against the biasing force of the biasing element from the self-weight of the head, so that the head supporting plate lowers to the lowest position, and the height thereof becomes the lowest. When the user rolls over and takes a posture of lying sideways, and the head is supported by the shoulder so that load acting on the head supporting plate decreases, the first and the second supporting members rise from the biasing force provided by the biasing element, and the height of the pillow increases until it becomes the state where the load from the head and the biasing force is balanced. Further, the pillow is equipped with an adjusting element for adjusting the biasing force by the biasing element, and is capable of adjusting the height during lying sideways. Moreover, the pillow is equipped with a stopper mechanism for stopping the supporting member at a predetermined tilt angle against the biasing force of the biasing element, so that the height during nonuse is uniform.

-   [Patent Document 1] Japanese Patent Laid-Open No. 2005-342457 -   [Patent Document 2] Japanese Patent Laid-Open No. 2004-57505 -   [Patent Document 3] Japanese Patent Laid-Open No. 2001-340198 -   [Patent Document 4] Japanese Patent Laid-Open No. 2007-98153

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, in the pillow disclosed in Patent Document 4, the height in the state where the load by the head and the biasing force of the biasing element balances is the height during lying sideways. Therefore, in order for the height during lying sideways be appropriate for the user, each user must adjust the biasing force of the biasing element in accordance with the body type, head weight and the like of each user. However, there is a problem that such adjustment is difficult. Further, the height of the pillow changes from slight variation of load by the head during sleep, so that the height during lying sideways becomes unstable. Therefore, there is a problem of giving soft and springy feeling to the user.

The present invention has been made in view of the above, and is aimed at providing a pillow whose height during lying on the back and lying sideways automatically and reliably changes depending on the sleeping posture of the user, which requires no adjustment, and which has stable height.

Means for Solving the Problem

The inventors of the present invention, upon conducting the invention, first unraveled that the order of the body abutting against the pillow and the position to which the load acts differ between the posture of lying on the back and the posture of lying sideways. That is, when a person lies down to the posture of lying on the back, such person lies on the back while pulling the neck upward and lift the head in order to protect one's valuable head by intuition. As a result, when a person lies down to the posture of lying on the back, the back, the neck, and the occipital region of the head in this order abuts against the bed or the pillow. On the other hand, when a person lies does to the posture of lying sideways, the side of the arm, the shoulder, and the temporal region of the head in this order abuts against the bed or the pillow. As a result, when a person lies down to the posture of lying sideways, the temporal region of the head first abuts against the pillow, so that the neck merely abuts against the pillow lightly.

Therefore, the load acting on the pillow in lying down to the posture of lying on the back first becomes the largest under the neck, and thereafter a part of the load transfers to under the occipital region of the head, and the load under the neck and under the occipital region of the head becomes approximately equal. That is, during lying on the back, first the load acts under the neck, and then the load is dispersed to under the head. On the other hand, the load acting on the pillow in lying down to the posture of lying sideways concentrates under the temporal region of the head, but almost no load acts under the neck. That is, during lying sideways, the load concentrates to under the temporal region of the head.

As such, the difference in load position by sleeping posture is unraveled, it became apparent that a pillow may descend smoothly during lying on the back and stably maintain its height during lying sideways, when it takes a structure enabling a front side portion of the pillow which is below the neck descends with light load and the center portion of the pillow which is below the temporal region of the head may bear larger load.

In this case, as the difference between the load capacity under the neck and under the temporal region of the head becomes larger, the smooth descend during lying on the back and the maintenance of the height during lying sideways becomes reliable, so that it does not depend on individual variation such as the body type and the head weight. Specifically, it is preferable when the load capacity of the rear side portion of the pillow is twice or larger than the load capacity of the front side portion. If the load capacity of each portion becomes such load, then it smoothly descends when a person with small body size and light head weight sleeps in the posture of lying on the back, and, it surely maintains the height when a person with large body size and heavy head weight sleeps in the posture of lying sideways. In a parallelogram link disclosed in the above-mentioned Patent Document 4, difference in load capacity between under the neck and under the temporal region of the head is hardly recognized, and there is a necessity for providing load capacity difference by the biasing force of the biasing element which biases the pillow upwards, and there is a necessity for performing delicate adjustment for each user.

In order to achieve the above-mentioned object, the pillow of the present invention comprises: a head placement member of a flat, approximately cuboid shape formed from a flexible member having a hollow therein; and a biasing device provided in the hollow for supporting the head placement member at an upper portion of the hollow of the head placement member by biasing upwards; wherein the biasing device is, when taking the side at which a neck is positioned in the state where a head of a person is positioned on the head placement member as a front side and the side at which a vertex of the head is placed as a rear side, equipped with a link mechanism comprised of a lower side link extending horizontally in a longitudinal direction, a front side link connected rotatably at a lower end portion thereof to a front end portion of the lower side link and which is tilted forward, a rear side link connected rotatably at a lower end portion thereof to a rear end portion of the lower side link and which is tilted forward, an upper side link connected rotatably at a front end portion thereof to an upper end portion of the front side link and connected rotatably at a rear end portion thereof to an intermediate portion of the rear side link, and a load supporting link with a rear end side thereof placed slidably on the upper end portion of the rear side link and a front end side thereof connected rotatably to a front end portion of the upper side link, a biasing element which biases the upper side link and the load supporting link so as to push the same upwards, and a regulating element which regulates tilting of the rear side link rearwards, wherein a link length of the front side link is longer than a link length of the rear side link, wherein in the state where the head of a person is not placed on the head placement member, a product of a sine of a tilt angle towards the front and the link length of the front side link is twice or larger than that of the rear side link, the tilt angle towards the front of the rear side link exceeds 0 degree and is equal to or smaller than 20 degrees, and the load supporting link is positioned at a most elevated position by being biased from the biasing element and by being supported by the upper end portion of the rear side link, and the biasing force of the biasing element is set so that the load supporting link descends to a most descended position when the front side link and the rear side link falls forward in the state where the head of a person is placed on the head placement member.

Effect of the Invention

According to the pillow of the present invention, in the state where the head of a person is not placed on the head placement member, the load supporting link is positioned at the most elevated position, and the head placement member supported by the load supporting link is also positioned at the most elevated position. Thereafter, when the head of a person is placed on the head placement member positioned at the most elevated position, the downward load from the self-weight of the head of a person acts on the load supporting link of the biasing mechanism via the head placement member. The load supporting link moves to deform downwardly from the load, but in order for the load supporting link to deform downwards, it is necessary to make the front side link and the rear side link fall forward from the configuration of the link mechanism, and also resist against the biasing force of the biasing element. The product of the sine of the tilt angle towards the front and the link length of the front side link is twice or larger than that of the rear side link. Therefore, when the same downward load acts on the upper end portion of the rear side link and the front side link, the rotational moment acting in the direction of making the front side link fall forward is twice or larger than the rotational moment acting in the direction of making the rear side link fall forward. Therefore, although there may be some difference according to the biasing force of the biasing element and the link length of each link, the load capacity (the load necessary for the load supporting link to commence downward displacement) of the rear side portion of the pillow is approximately twice or larger than the load capacity of the front side portion. Therefore, the load bearing link is easier to deform downwards as the acting position of the load acting downwardly on the head placement member is more towards the front side, and the load bearing link is more difficult to deform downwards as the same is more toward the rear side.

If the rear side link is perpendicular or tilted rearwards, it becomes easier to fall rearward which is opposite to the direction the front side link falls, so that there is a fear that the link mechanism may break. Therefore, the tilt angle towards the front of the rear side link must exceed 0 degree. On the other hand, if the front side link is steeply tilted forward, it is not preferable because the front side link falls forward even when a slight load acts on the front side portion of the head placement member, and also it becomes too long in the longitudinal direction of the pillow in order to configure the link mechanism. The tilt angle towards the front of the front side link must be in an appropriate range taking these into consideration, and it is preferable that the tilt angle towards the front of the rear side link is 20 degrees or smaller. Therefore, it is preferable that the rear side link is in a forward-falling substantially vertical state in which the tilt angle towards the front is over 0 degree and 20 degrees or smaller.

As explained above, the load concentrates under the temporal region of the head when lying in the posture of lying sideways. Under the temporal region of the head is the center in the longitudinal direction of the head placement member, and a similar downward load acts on the upper end portion of the front side link and the rear side link. By the action of these load, the front side link tends to fall forward, but the rear side link tends to maintain the forward-falling substantially vertical state. Because the front side link and the rear side link are connected via the upper link, the front side link does not fall forward unless the rear side link falls forward. As a result, the front side link and the rear side link does not fall forward, and the load supporting link maintains the most elevated position. Therefore, the head placement member does not descend, and merely deflects by the self-weight of the head, and maintains the most elevated position. This position is stable without moving vertically even when the load acting from the head to the head placement member varies to a certain extent.

On the other hand, when lying in the posture of lying on the back, the load concentrates first under the neck. Under the neck is the front side of the head placement member, so that large downward load acts on the tipper end portion of the front side link, and approximately no load acts on the upper end portion of the rear side link. By the action of these loads, the front side link tends to fall forward with a large force, and tends to make the rear side link connected via the upper link fall forward. As a result, the front side link and the rear side link falls forward, and the load supporting link descends thereby. Once the load supporting link descends, it automatically descends to the most descended position against the biasing force from the biasing element. Therefore, the head placement member descends to the most descended position accompanied by the load supporting member. This position is stable without moving vertically even when the load acting from the head to the head placement member varies to a certain extent.

Further, the biasing element may be one generating biasing force to the extent that the load supporting link does not descend from the self-weight of the head placement member, and to the extent not preventing the load supporting link from descending once it has started to descend. The biasing element is not for adjusting the height during lying sideways by the biasing force, as is the case with the biasing element disclosed in the above-mentioned Patent Document 4, so that there may be variation to a certain extent in the generated biasing force. Therefore, maintenance of the biasing force by the biasing element is simplified, and the manufacturing of the pillow becomes easier.

Further, because the regulating element for regulating the tilting of the rear side link rearward is provided, it becomes possible to prevent link mechanism from breaking by the front side link falling forwards and the rear side link falling rearwards.

It is preferable that, in the state where the head of a person is not placed on the head placement member, upper surfaces of the load supporting link and the head placement member are tilted upwards toward the front.

In this case, when the head is placed on the pillow in the posture of lying on the back, it is further made certain for the neck to abut against the pillow before the occipital region of the head. Therefore, the load supporting link automatically and more reliably descends to the most descended position during lying on the back.

Further, it is preferable that the biasing element is a tension spring with one end side being fixed to a portion of the load supporting link extended forward from a rotatable connecting portion with the front side link, and other end side being fixed to a vicinity of the rear end portion of the lower side link.

In this case, the load supporting link has one end side of the tension spring fixed to the portion extended forward from the rotatable connecting portion, so that it is operated to lower the above-mentioned extended portion and the portion rearward from the rotatable connecting portion is raised by the biasing force of the tension spring. When a person sleeps in the posture of lying on the back, the above-mentioned portion rearward from the rotatable connecting portion is raised by the load acting under the neck, the contact pressure between the load supporting link and the upper end portion of the rear side link becomes smaller, so that the load supporting link becomes easier to slide and become more easier to descend.

Further, it is preferable that the pillow is configured so as to make an impact absorbing member positioned between the lower side link and each of the front side link and the rear side link, respectively, when the front side link and the rear side link fall forward.

In this case, it becomes possible to suppress the impact and abutment sound generated from the front side link and the rear side link abutting against the lower side link.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an external appearance of a pillow according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1;

FIG. 3 is a cross-sectional view taken along line in FIG. 1;

FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2;

FIG. 5 is an upper view of the pillow with a part taken away;

FIG. 6 is a side view of a link mechanism at a most elevated state;

FIG. 7 is a side view of the link mechanism at a most descended state;

FIG. 8 is a longitudinal cross-sectional skeleton view of the pillow during lying on the back;

FIG. 9 is a horizontal cross-sectional skeleton view of the pillow during lying on the back;

FIG. 10 is a longitudinal cross-sectional skeleton view of the pillow during lying sideways; and

FIG. 11 is a horizontal cross-sectional skeleton view of the pillow during lying sideways.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of a pillow according to the present invention will now be explained below with reference to the accompanying drawings.

As shown in FIG. 1 through FIG. 5, a pillow 1 includes a flat, substantially cuboid-shaped head placement member 2 formed from a flexible member including a hollow 2 a therein, a cap member 3 arranged at a rear side of the head placement member 2 and which covers the rear side of the hollow 2 a of the head placement member 2, and a biasing device 4 provided in the hollow 2 a so as to bias and support an upper portion 2 b of the hollow 2 a of the head placement member 2 upwards. Here, in the situation where a head of a person is placed on the pillow 1, the side where a vertex of the head is positioned is referred to as the rear side, and the side where a neck of a person is positioned is referred to as the front side. Further, the whole outer side of the pillow 1 is covered by an outer cover cloth 5, in the state where the biasing device 4 is provided inside the hollow 2 a and the cap member 3 is adhered to the rear end of the head placement member 2.

The head placement member 2 is formed from the flexible member. In the present embodiment, the head placement member 2 is formed from a formed body made of a low-resilience urethane foam. The low-resilience urethane foam is familiar as a material for pillows, because it is low in resilience and is superior in adaptability. However, the head placement member 2 may be made of a high-resilience urethane foam. As is shown in FIG. 1 and FIG. 5, the external appearance of the head placement member 2 takes a flat, substantially cuboid-shape, which has an approximately rectangle shape which is horizontally long when seen from above, and as is shown in FIG. 2 and FIG. 3, formed so that the upper surface is inclined upward towards the front, the lower portion of the front side is inclined rearward, and the front upper corner is rounded with a large radius of curvature. The shape of the head placement member 2 needs only be formed in a flat, substantially cuboid-shape. It is not limited to the shape in the figures, and may be, for example, oval shape when seen from above.

The hollow 2 a is formed to be opened at the rear side. The head placement member 2 is formed with a number of air holes 2 c which communicate the hollow 2 a with the exterior at the center portion of the upper portion 2 b of a hollow part 2 a, thereby preventing heat from being accommodated in the hollow 2 a. The outer cover cloth 5 positioned above the air holes 2 c is provided with a three-dimensional knitting 5 a (refer to FIG. 2 through FIG. 4), so as to exert ventilation from the air holes 2 c to the region where the air holes 2 c does not exist. Further, the vertical speed of the pillow 1 is made appropriate, by the ventilation volume of the air inside the hollow 2 a via the air holes 2 c.

In order to avoid a person from having a feeling of strangeness by sensing the presence of the biasing device 4 arranged inside the hollow 2 a when a head of a person is placed on the pillow 1, the upper portion 2 b of the hollow 2 a of the head placement member 2 is required to have a predetermined thickness or more, for example a thickness in the range of 2 cm to 3 cm. However, if the overall height of the pillow 1 is too high, it is not preferable because a sufficient lowness is not obtained during lying on the back. Therefore, the thickness of the head placement member 2 at a lower portion 2 d of the hollow 2 a is set to be thinner than the thickness of the head placement member 2 at the upper portion 2 b of the hollow 2 a. The thickness of the lower portion 2 d of the hollow 2 a is preferably thinned to, for example, about 1 cm. However, when the thickness of the lower portion 2 d of the hollow 2 a is thinned, sufficient strength is not obtained, and is easily ripped especially during forming. Therefore, by forming the head placement member 2 by covering a cloth 2 e to the outer periphery of an inner mold for the hollow 2 a, the head placement member 2 is reinforced by adhering the cloth 2 e to overall inner surface of the hollow 2 a. Further, by providing the cloth 2 e, it becomes possible to prevent air leakage from other than the air holes 2 c of the head placement member 2, and prevent excessive ballooning or breakage of the hollow 2 a.

Meanwhile, the upper surface of the head placement member 2 of the pillow 1 easily fits the head of a person if it is made into a curved surface coinciding with a convex-concave curving line from the rear surface of the neck of a person to the occipital region of the head during tying on the back. On the other hand, the upper surface of the head placement member 2 of the pillow should be flat in order to be suitable for the temporal region of the head during lying sideways. In order to solve this inconsistency, the upper surface of the head placement member 2 is made flat, and the upper portion 2 b of the hollow 2 a is formed into a curved surface in which the convex-concave curved surface from the rear side of the neck to the occipital region of the head is turned upside down, as is shown in FIG. 3. More specifically, a convex-concave shape from a front side portion of a lower surface of a laterally center portion of the upper portion 2 b of the hollow 2 a of the head placement member (hereinafter referred to as an upper portion lower surface front side portion) 2 f to a center portion thereof (hereinafter referred to as an upper portion lower surface center portion) 2 g is formed so as to turn upside down the rear side curve shape of the neck to the occipital region of the head of a human when viewed from the side. That is, the upper portion lower surface front side portion 2 f is increased in thickness and the lower surface thereof projects downward, to match the depressed shape of the rear side of the neck, and the upper portion lower surface center portion 2 g is decreased in thickness and the lower surface thereof is depressed, to match the protruding shape of the occipital region of the head. By doing so, in the case where the biasing device 4 becomes extremely thin and the hollow 2 a approximately disappears during lying on the back (refer to FIG. 8), the upper surface of the pillow 1 becomes a shape along the shape from the rear surface of the neck to the occipital region of the head of the user. Therefore, the user is capable of sleeping without receiving excess repelling force from the head placement member 2.

As with the head placement member 2, the cap member 3 is made of the flexible member, and in the present embodiment, is formed from a formed body made of a low-resilience urethane foam. The cap member 3 has a thickness nearly equal to that of a front side portion 2 h of the head placement member 2. The cap member 3 is formed into a flat approximately cuboid-shape which is short in the longitudinal direction, with the front end surface thereof shaped to match the shape of the rear end surface of the head placement member 2. The rear end surface of the head placement member 2 is formed approximately vertically, and the hollow 2 a is sealed by the cap member 3 by matching the front end surface of the cap member 3 to this rear end surface, and adhering and fixing the matched surface with an adhesive and the like, in the state where the biasing device 4 and the like are placed inside the hollow 2 a. Because the cap member 3 is positioned at the rear side end portion of the pillow 1, the head is not placed thereon, so that even if adhesive and the like harden, the user will not feel the presence thereof. Therefore, it becomes possible to reduce the height of the pillow 1.

The biasing device 4 is provided with a pair of link mechanisms 6, 6 spaced apart in the lateral direction in the hollow 2 a. With reference to FIG. 6, each link mechanism 6 comprises a lower side link 7 extending horizontally in the longitudinal direction, a front side link 8 with the lower end portion thereof being connected rotatably to the front end portion of the lower side link 7, a rear side link 9 with the lower end portion thereof being connected rotatably to the rear end portion of the lower side link 7, an upper side link 10 with the front end portion being connected rotatably to the upper end portion of the front side link 8 and the rear end portion thereof being connected rotatably to the intermediate portion of the rear side link 9, and a load supporting link 11 with the rear portion being placed slidably on the upper end portion of the rear side link 9 and the front portion thereof being connected rotatably to the front end portion of the upper side link 10. The rear side link 9 is configured to stand in a predetermined forward-falling substantially vertical state, that is, to have a tilt angle β in a forward direction of exceeding 0 degree to 20 degrees or less, preferably 3 degrees or more to 15 degrees or less. On the other hand, a tilt angle α in the forward direction of the front side link 8 is configured to be larger than the tilt angle β in the forward direction of the rear side link 9. More specifically, it is configured so that the product of the sine of the tilt angle α in the forward direction of the front side link 8 and the link length of the front side link 8 becomes twice, preferably two-and-a-half times larger than the product of the sine of the tilt angle β in the forward direction of the rear side link 9 and the link length of the rear side link 9. Further, the front side link 8 is configured so that the load supporting link 11 is tilted upwards toward the front, and the link length of the front side link 8 is made longer than the link length of the rear side link 9. When the biasing device 4 is arranged in the hollow 2 a, the load supporting link 11 faces the upper portion 2 b of the hollow 2 a.

The lower side link 7, the front side link 8, the rear side link 9, and the load supporting link 11 are each formed from elongated metal plate having identical width. Although not shown, each links of the lower side link 7 and the front side link 8, and the front side link 8 and the load supporting link 11, are connected rotatably by a hinge mechanism. The lower side link 7 and the rear side link 9 are connected rotatably by a pin mechanism, using rear side link fixing pieces 7 a, 7 a formed integrally so as to project upward from the left and right side end portions of the rear end portion of the lower side link 7. On the other hand, the upper side link 10 is formed from a pair of elongated metal plates spaced apart to a distance exceeding the width of the lower side link 7 and the like. The rear end portion of the upper side link 10 is connected rotatably by a pin mechanism to upper link fixing pieces 9 a, 9 a formed integrally so as to project forward from the left and right side ends of the intermediate portion of the rear side link 9. Further, the front end portion of the upper side link 10 is connected rotatably by a pin mechanism to upper link fixing pieces 11 a, 11 a, formed integrally so as to project downward from left and right side ends of the front end portion of the load supporting link 11. The load supporting link 11, 11 is configured so as to project downward from the upper portion lower surface front side portion 2 d of the head placement member 2 when seen from the side, and the overall height of the pillow 1 is reduced.

The rear side link 9 is equipped with a sliding portion 9 b coated with a low-friction material such as a polytetrafluoroethylene, at an upper end portion of the rotatable connecting portion with the upper side link 10 which is extended upwardly. The load supporting link 11 is placed on top of the sliding portion 9 b. Because the sliding portion 9 b is coated with the low-friction material, the load supporting link 11 smoothly slides on the sliding portion 9 b in the longitudinal direction, and also the noise generated during sliding is suppressed. The sliding portion 9 b may not necessarily be coated with the low-friction material, and the top end portion of the sliding portion 9 b may be rounded instead.

As shown in FIG. 4 and FIG. 5, both left and right lower side links 7, 7 are connected in parallel to each other so as to maintain a predetermined distance in the horizontal direction by a lower connecting member 12. The lower connecting member 12 is comprised of a thin rectangular-shaped metal plate, and connects extended portions 7 b, which are both lower side link 7, 7 extended rearward from the rotatable connecting portions with the rear side links 9, 9, by being fixed by welding or the like. Both left and right rear side links 9, 9 are connected in parallel to each other so as to maintain a predetermined distance in the horizontal direction by an intermediate connecting member 13. The intermediate connecting member 13 is comprised of a thin rectangular-shaped metal plate, and connects the portions positioned between the rotatable connecting portion between the lower side links 7, 7 and the rotatable connecting portion between the upper side links 10, 10, of the both rear side links 9, 9, by being fixed by welding or the like. Both left and right load supporting links 11, 11 are connected in parallel to each other so as to maintain a predetermined distance in the horizontal direction by an upper connecting member 14. The upper connecting member 14 is comprised of a thin rectangular-shaped metal plate, and connects the portions of the load supporting links 11, 11 rearward from the portions contacting with each sliding portion 9 b of the rear side links 9, 9. Each of the connecting members 12, 13, and 14 may be formed integrally with each of the links 7, 9, and 11, respectively.

Each link mechanism 6 configured as mentioned above is, as is shown in FIG. 2, FIG. 3 and FIG. 6, equipped with the lower side link 7 receiving overall load of the head, the front side link 8 largely tilting forward so as to easily fall towards the front side with a small downward load, the rear side link 9 standing in the forward-falling substantially vertical state so as to be capable of enduring a large downward load, and the upper side link 10 connecting the front side link 8 and the rear side link 9. These links 7, 8, 9, and 10 are connected rotatably to one another, and constitutes an approximately oblong link. However, the movement amount at the time of falling differs between the front side link 8 having large tilt angle β and the rear side link 9 having small tilt angle α and which is in the forward-falling substantially vertical state. Therefore, in the case where an upper rotatable portion of the rear side link 9 and an upper rotatable portion of the front side link 8 are connected by the upper side link 10 to match the front side link 8 having small movement amount, the upper side link 10 becomes a rearward inclined state to a great extent. Therefore, if the upper side link 10 is used as the link supporting the upper portion 2 b of the hollow 2 a of the head placement member 2, there arises an inconvenience that the upper surface of the pillow 1 tilts greatly. Therefore, in the link mechanism 6 of the pillow 1, in order to prevent the supporting link from becoming a rearward inclined state to a great extent, and also to make the link mechanism 6 thin at the most descended state, the rear side link 9 is extended further upward from the rotatable connecting portion with the upper side link 10, the load supporting link 11 is placed slidably on the sliding portion 9 b which is an upper end portion of the extension, and the front portion of the load supporting link 11 is connected rotatably to the front end portion of the upper side link 10. By configuring the link mechanism 6 this way, the load supporting link 11 becomes the link supporting the upper portion 2 b of the hollow 2 a of the head placement member 2, and it becomes possible to arbitrarily set the tilt thereof close to horizontal.

As is shown in FIG. 2 to FIG. 5, the biasing device 4 is equipped with tension springs 15, 15 as a biasing element for biasing the upper side links 10, 10 and the load supporting links 11, 11 to push upward. Each tension spring 15 is tightened by fixing one end side to an outer side of the lower side link 7 rearward from the rotatable connecting portion with the rear side link 9, and the other end side to an outer side of the load supporting link 11 forward from the rotatable connecting portion with the front side link 8. A hook on the one end side of the tension spring 15 is hooked to a hole on a spring fixing piece 7 c, which is integrally formed so as to project upward from both outer end portions of the extended portion 7 b of the lower side link 7. Further, the hook on the other end side of the tension spring 15 is hooked to a hole on a spring fixing piece 11 c, which is integrally formed so as to project downward from both outer ends of the extended portion 11 b extended forward from the rotatable connecting portion with the front side link 8. By doing so, the tension spring 15 biases the load supporting link 11 to push upward, and as well as the front side link 8 to rise upright.

Further, because the front end of the tension spring 15 is fixed to the extending portion 11 b which projects forward from the rotatable connecting portion, the load supporting link 11 is operated so that the extending portion 11 b descends by the biasing force of the tension spring 15, and the main body rearward of the rotatable connecting portion is lifted up. As a result, the contact pressure between the load supporting link 11 and the sliding portion 9 b becomes small, so that it becomes easier for the load supporting link 11 to slide on the sliding portion 9 b.

The biasing device 4 is equipped with stoppers 16, 16 as a regulating element for regulating the rear side links 9, 9 from tilting rearwardly. Each stopper 16 is provided on the lower side link 7 in the vicinity of the rotatable connecting portion with the rear side link 9. In the present embodiment, the stopper 16 is configured by bending a leading end portion of the lower side link 7 which is projected upwardly from a rear portion of the rear side link fixing piece 7 a for rotatable connection with the rear side link 9 inwardly. However, the stopper may be provided rearward of the load supporting link 11. By the rear side link 9 abutting against a folded front end surface 7 d, the rear side link 9 is regulated from tilting rearwardly from a predetermined forward-falling substantially vertical state. If the rear side link 9 becomes a rearward-falling state, it becomes easy for the rear side link 9 to fall rearwardly, which is the direction opposite to the front side link 8, so that there is a fear that the link mechanism 6 is damaged. The stopper 16 prevents this from happening.

The biasing device 4 is equipped with impact absorbing blocks 17, 17, which absorb the impact generated by the falling of the front side links 8, 8 and the rear side links 9, 9, when the load supporting links 11, 11 descends, and to suppress impact noise generated thereby. The impact absorbing blocks 17, 17 are formed from the flexible member, and in the present embodiment, are formed from a formed body made from low-resilience urethane foam. The impact absorbing blocks 17, 17 are provided so as to be positioned between the lower side link 7 and each of the front side link 8 and the rear side link 9 when each links 8, 9 falls, and in the present embodiment, is provided by being fixed to the upper surface of the lower side link 7 by an adhesive and the like. The impact absorbing blocks 17 for the front side link 8 is provided on the upper surface of an extended portion 7 e of the lower side link 7 extended forward from the rotatable connecting portion with the front side link 8. The impact absorbing blocks 17, 17 may be formed by being fixed to the lower surface of the front side link 8 or the rear side link 9 by an adhesive and the like. When the front side link 8 and the rear side link 9 falls, and each link 8, 9 flexes the impact absorbing blocks 17, 17 to its minimum thickness, the position of the load supporting link 11 at this time becomes the most descended position. Further, because the flexed impact absorbing blocks 17, 17 have restoring force, the impact absorbing blocks 17, 17 provide biasing force so as to displace the front side link 8 and the rear side link 9 upward, and assist the upward biasing by the tension springs 15, 15. Here, spring members such as a coil spring and a flat spring may be used as the impact absorbing blocks 17, 17.

Further, the biasing device 4 is attached with a lower plate 18, an upper plate 19, a meshed cloth 20, a sponge member 21, and a flexible sheet 22. The lower plate 18 is formed of a rigid resin plate comprised of a PET (polyethylene terephthalate) and the like, and is formed into a shape in which a front portion and a center portion which is positioned downward of the head to be placed on the upper surface of the pillow 1 is cut out from a substantially rectangular shape which is substantially identical to the lower surface of the hollow 2 a, that is, a substantially U-shape with the front side opened. The lower plate 18 is fixed to the lower surface of the lower side links 7, 7 and the lower connecting member 12 by rivets or the like not shown. By placing the lower plate 18 to the lower surface of the hollow 2 a, it becomes possible to place the biasing device 4 to a predetermined position within the hollow 2 a. As such, because the lower surface of the lower side links 7, 7, and the lower connecting member 12, that are thin metal members, is covered with the lower plate 18, the user does not perceive the presence of metal members from below the pillow, so that the user senses no uncomfortable feeling.

The upper plate 19 is formed of a rigid resin plate comprised of a PET and the like, covers the upper surface of the load supporting links 11, 11 and the upper connecting member 14, and is formed into a substantially U-shape by cutting out the front portion and the center portion similarly to the lower plate 18. The upper plate 19 is fixed to the upper surface of the load supporting links 11, 11 and the upper connecting member 14 by rivets and the like not shown. As such, because the upper surface of the load supporting links 11, 11 and the upper connecting member 14, that are thin metal members, is covered with the upper plate 19, the user does not perceive the presence of metal members from above the pillow, so that the user senses no uncomfortable feeling.

The meshed cloth 20 is stretched across the upper plate 19 at an appropriate strength so as to supplement the cut-out front portion and the center portion, and supports the head and prevents large drop of the head when lying sideways. As mentioned above, the upper portion lower surface front side portion 2 d of the head placement member 2 is projected downwards. It is preferable to match the projection position to the position under the center portion where the meshed cloth 20 is stretched. In this case, even when the meshed cloth 20 is stretched loosely in order to lower the height of the pillow 1 at the most descended state, the center portion of the planar upper surface of the pillow does not dent when not in use. Therefore, it becomes possible to obtain the pillow 1 of a neat overall shape.

The sponge member 21 is formed from a high-resilience urethane form as the flexible member, and is provided so as to be positioned at the uppermost surface of the biasing device 4. Therefore, even if the head placement member 2 is made sufficiently soft, and also the upper portion 2 b of the hollow 2 a is thinned to a certain extent, the user does not feel the hardness of the upper plate 19 from above the pillow. The sponge member 21 is formed with air holes communicating with the air holes 2 c of the head placement member 2.

The flexible sheet 22 is formed from a single soft resin sheet made of urethane or the like, and is stretched laterally between the front upper surface of the load supporting links 11, 11 and the front lower surface of the lower side links 7, 7. The flexible sheet 22 reinforces the front side portion of the meshed cloth 20, and as well as improves the touch of the pillow 1 contacting the shoulder portion of the user when lying sideways, by forming an arc shape projecting forward.

The pillow 1 configured as explained above is, when not in use where nothing is placed thereon, biased by the biasing force (tensile force) of the tension springs 15, 15 so as to lift up the load supporting links 11, 11. Further, the rear portion of the load supporting links 11, 11 is supported by the sliding portion 9 b at the upper end of the rear side links 9, 9, so that the rising of the rear side links 9, 9 is regulated. Therefore, the upper surface of the pillow 1 eventually exists at the most elevated position. The height of the pillow 1 at that state is suitably from 8 cm to 16 cm, for example.

In the pillow which automatically lifts and drops, there was a big problem of obtaining sufficient lowness suitable for lying on the back when the upper surface of the pillow descends to its lowermost. Therefore, it is preferable for the biasing device 4 which is provided inside the pillow 1 and which performs lifting and dropping to be as thin and low as possible in the most descended state. The distance between an occipital region of a head of a person lying on the back and the bed is approximately 2 cm to 5 cm, which vary among individuals, and a person feels strange if a rigid member is provided therebetween. Therefore, the head is supported by soft materials such as the meshed cloth 20. However, if the both sides of the pillow are high when the biasing device 4 descends to its lowermost, the lowness of approximately 2 cm cannot be obtained unless the meshed cloth 20 is stretched across considerably loosely. But when the meshed cloth 20 is stretched across loosely, the temporal region of the head drops excessively when the pillow is elevated and the person lies sideways, so that the person feels strange. This can be solved by stretching the meshed cloth 20 tightly across, but in order to do so, it is desirable for the biasing device 4 at its most descended state to have a height of 1 cm or less.

Therefore, the biasing device 4 of the pillow 1 is provided so that the upper side link 10 is, as is explained above, positioned so as to be paired in laterally outwardly sandwiching the other links 7, 8, 9, 11, when the front side links 8, 8 and the rear side links 9, 9 falls down and the load supporting links 11, 11 descends. Therefore, the upper side link 10 does not interfere with the other links 7, 8, 9, 11, and the biasing device 4 becomes extremely thin.

Further, when the difference between the load capacity of the front side portion 1 a of the pillow 1 to which the neck is placed and the load capacity of the center portion 1 b to which the temporal region of the head is placed becomes larger, the smooth descending during lying on the back and the height maintenance during lying sideways becomes more reliable. Therefore, it is preferable because the rising and falling will not depend on physical shape or head weight which vary among individuals. As a result of experiments, it was proven that the load capacity of the front side portion 1 a to be 4 kg, and the load capacity of the rear side portion 1 b to be twice or larger than the front side portion 1 a, that is, 8 kg or more, to be successfully not depend on individual variation. And the load capacity of each part may easily be obtained by making the product of the sine of the tilt angle α of the front side links 8, 8 and the link length be twice or larger than the product of the sine of the tilt angle β, of the rear side links 9, 9 and the link length, and to make the tension springs 15, 15 which biases upward to have an appropriate strength. Therefore, by setting the tilt angle α and the link length of the front side links 8, 8, the tilt angle β and the link length of the rear side links 9, 9, and the strength of the tension springs 15, 15 so that the load capacity of each part 1 a, 1 b becomes the above-mentioned load, it becomes possible to obtain the biasing device 4 capable of smoothly descending to its lowermost position when a small person with light head weight lies on the back, and capable of reliably maintaining the uppermost position when a large person with heavy head weight lies sideways, without adjusting the biasing force of the tension springs 15, 15. Therefore, further, because the pillow 1 does not need an adjustment mechanism therein, the manufacturer is capable of making the pillow lighter and as well as mass-production at low cost. The term the pillow 1 or a biasing element 4 smoothly rises and falls means that the same rises and falls with small resilient force, without abrupt speed change, and at an appropriate speed so as not to disturb the user's sleep.

As is explained above, the pillow 1 is capable of automatically obtaining sufficient height during lying sideways and as well as obtaining sufficient lowness suitable for lying on the back, and capable of solving troubles especially the middle-aged people with a decline in physical performances have against pillows. Further, similar to selecting the size of a shirt and shoes, by selecting the appropriate type of pillow 1 from a previously prepared types with a combination of height (most elevated position) and lowness (most descended position), the user is capable of using the pillow suitable for lying on the back and lying sideways, without performing troublesome adjustment. It becomes possible to provide pillows suitable to people of approximately all body type and head weight, by preparing 9 types of pillows with a combination of 3 types of height and 3 types of lowness. The change in height may be performed, for example, by changing the link length of the front side links 8, 8, the rear side links 9, 9, and the upper side links 10, 10. On the other hand, changing the lowness may be performed, for example, by providing a leveling member to the lower surface of the pillow 1, changing the thickness of the lower portion 2 d of the hollow 2 a of the head placement member 2, and changing the thickness of the impact absorbing blocks 17, 17.

Next, the operation of the pillow 1 when placing the head on the upper surface of the pillow 1 in order to lie down in the posture of lying on the back will be explained below. In general, when a person lies in the posture of lying on the back, such person pull the neck in order to protect one's valuable head by intuition, so that the occipital region of the head is lifted to touch the pillow 1 last. As a result, one's back first abut against the bed, and then abut against the pillow 1 in the order of lower neck and occipital region of the head. As shown in FIG. 2 and the like, the front side portion 1 a of the pillow 1 to which the lower neck abut against is higher than the center portion 1 b to which the occipital region of the head abut against by about 2 cm to 4 cm. Therefore, when a person lies on the back, the neck is first placed on the front side portion 1 a of the head placement member 2, and thereafter the occipital region of the head is placed on the center portion 1 b of the head placement member 2. The upper surface of the pillow 1 and the load supporting links 11, 11 are tilted so as to tilt upwards toward the front, the front side portion of the load supporting links 11, 11, in particular the extended portion 11 c forward from the rotatable connecting portion with the front side links 8, 8, receives large load from the neck, and the rear side portion of the load supporting links 11, 11 slightly becomes lifted taking the rotatable connecting portion as the axis. As a result, the contact pressure between the load supporting links 11, 11 and the sliding portion 9 b of the rear side links 9, 9 becomes small and the load supporting links 11, 11 becomes easier to slide, and the rear side links 9, 9 standing substantially perpendicular becomes easier to fall forward. Further, at this time, because the product of the sine of the tilt angle α in the forward direction of the front side links 8, 8 and the link length thereof is twice or larger than the product of the sine of the tilt angle β in the forward direction of the rear side links 9, 9 and the link length thereof, a large forward rotational moment acts on the front side links 8, 8. Therefore, the front side links 8, 8 further becomes easier to fall forward. As a result, it becomes easier for the load supporting links 11, 11 to descend, and the upper surface of the head placement member 2 to sink, the pillow 1 with the head of a person in the posture of lying on the back smoothly sinks.

When the front side links 8, 8 falls forward, tensile force of the tension springs 15, 15 acts as a repelling force against the fall. However, the tension springs 15, 15 are set to generate a repelling force to the extent so as not to prevent smooth forward falling of the front side links 8, 8, so that it does not prevent the pillow 1 with a head of a person lying on the back being placed from sinking.

When the upper surface of the pillow 1 sinks, the front side links 8, 8 and the rear side links 9, 9 abut against the peak of the impact absorbing blocks 17, 17, and thereafter fall down while flattening the impact absorbing blocks 17, 17. Therefore, because the front side links 8, 8 and the rear side links 9, 9 does not directly contact the lower side links 7, 7, it becomes possible to prevent the abutting noise, and as well as to suppress the impact generated when the links 8, 9 falls to its maximum and the upper surface of the pillow 1 sinks to its most descended position, as is shown in FIG. 8 and FIG. 9. The flattened impact absorbing blocks 17, 17 generate restoring force which prevents falling of the links 8, 9 as the same is flattened further, the impact absorbing blocks 17, 17 are set to generate restoring force to the extent so as not to prevent smooth forward falling of the front side link 8 or the rear side link 9, so that it does not prevent the pillow 1 with a head of a person in the posture of lying on the back being placed from sinking.

Further, when the upper surface of the pillow 1 sinks, the volume of the hollow 2 a decreases and the air inside the hollow 2 a flow out to the outside via the air holes 2 c. Therefore, by arbitrarily forming the number and the size of the air holes 2 c and setting the air flow out amount per unit time, the rise-fall speed of the upper surface of the pillow 1 may be set appropriately. As such, it becomes possible to suppress abrupt up-and-down movement, and as well as suppress the impact generated when the upper surface of the pillow 1 sinks to its most descended position. Further, with the up-and-down movement of the upper surface of the pillow 1, the hollow 2 a repeats expansion and contraction, and large amount of air inside the hollow 2 a is taken in and exhausted from the air holes 2 c. Therefore, heat and moisture of the upper part of the pillow 1 decrease, so that sleeping becomes more comfortable.

Further, when a person sleeps while placing the head on the upper surface of the pillow 1, the lower surface of the upper portion 2 b of the hollow 2 a of the head placement member 2 comprised of a formed body made of low-resilience urethane foam sinks further down than the upper surface of the link mechanism 6, 6 made of metal member from the self-weight of the head. Further, below the head and neck when viewed from above, the head placement member 2, the outer cover cloth 5, the meshed cloth 20, the sponge member 21 and the flexible sheet 22 exist, but these are all formed from soft members, and no rigid members exist. Therefore, when a person sleeps while placing the head on the upper surface of the pillow 1, the person does not sense the rigid member beneath and feel uncomfortable, and also obtains soft touch. Further, because no rigid member exists beneath the head or the neck, soft touch can be obtained without thickening the thickness of the upper portion 2 b of the hollow 2 a of the head placement member 2. Moreover, because soft touch can be obtained without using the head placement member 2 with thick upper portion 2 b of the hollow 2 a, the height of the pillow 1 can be suppressed low.

Next, the operation of the pillow 1 when a person places the head on the upper surface of the pillow 1 in order to lie in the posture of lying sideways will be explained. In general, when a person lies sideways, the side of the arm and the shoulder first abut against the bed in order to receive body weight, and then the temporal region of the head is placed on the center portion 1 b of the pillow 1. As shown in FIG. 10, the difference of height between the temporal region of the head and the shoulder is large during lying sideways, majority of the load of the head is received by the center portion 1 b of the pillow 1, and a part of the load of the head is supported by the shoulder via the neck. The upper surface of the pillow 1 is tilted to rise towards the front. However, during lying sideways, the neck is more depressed than the temporal region of the head, so that load received by the front side portion 1 a of the pillow 1 under the neck which has little load capacity is small. Majority of the load of the head is received by the rear side links 9, 9, via the meshed cloth 20 and the load supporting links 11, 11. The rear side links 9, 9 stands substantially upright, so that the forward rotational moment from the load by the head received from above is small, so that it is difficult to fall forward. As a result, the rear side links 9, 9 is maintained in the state of standing substantially upright, so that the load supporting links 11, 11 does not descend and are maintained stably at the most elevated position. Therefore, the height of the pillow 1 during lying sideways becomes stable, and does not give soft and springy feeling to the user. Because of the height of the side of the shoulder, it is impossible to place load under the neck even intentionally during lying sideways.

Next, the operation of the pillow 1 when a person rolls over from lying sideways to the posture of lying on the back will be explained. During lying sideways, as is shown in FIG. 10 and FIG. 11, the load supporting links 11, 11 are in the most elevated position. From this state, when the user pulls the shoulder from the abutment position from the bed and takes the posture of lying on the back, the load supporting links 11, 11 sinks to the most descended position, as is the case with the posture of lying on the back explained above, as is shown in FIG. 8 and FIG. 9. As is apparent, even when a user rolls over from lying sideways to the posture of lying on the back, the load supporting links 11, 11 automatically deforms to the most descended position suitable for lying on the back, so that the user can obtain comfortable sleep thereafter.

Next, the operation of the pillow 1 when a person rolls over from lying on the back to the posture of lying sideways will be explained. During lying on the back, as is shown in FIG. 8 and FIG. 9, the load supporting links 11, 11 are in the most descended position. From this state, when the user turns sideways and pushes the shoulder inwards, the self-weight of the head does not work on the load supporting links 11, 11, or becomes extremely small, because the shoulder supports the head. At this time, the load supporting links 11, 11 automatically displaces upwards by the biasing force of the tensile springs 15, 15, and the restoring force of the impact absorbing blocks 17, 17. Then, as is shown in FIG. 10 and FIG. 11, the load supporting links 11, 11 displace to the most elevated position, and automatically stop at that position via the stoppers 16, 16. As is apparent, even when a user rolls over from lying on the back to the posture of lying sideways, the load supporting links 11, 11 deform to and automatically stop at the most elevated position suitable for lying sideways, so that the user can obtain comfortable sleep thereafter.

With respect to the current situation where people sleeping in the posture of lying sideways is increasing, if the pillow 1 is turned front side back and is used so that the rear side links 9, 9 are below the neck, it becomes possible to reliably maintain the height suitable for lying sideways, even in the sleeping posture where the temporal region of the head is barely placed on the pillow 1. In this case, the smoothness of the pillow 1 sinking will be slightly inferior when sleeping in the posture of lying on the back, however this becomes no problem by getting used to. The pillow automatically changes to the lowness suitable for lying on the back. 

1. A pillow, comprising: a head placement member of a flat, approximately cuboid shape formed from a flexible member having a hollow therein; and a biasing device provided in the hollow for supporting the head placement member at an upper portion of the hollow of the head placement member by biasing upwards; wherein the biasing device is, when taking the side at which a neck is positioned in the state where a head of a person is placed on the head placement member as a front side and the side at which a vertex of the head is positioned as a rear side, equipped with a link mechanism comprised of a lower side link extending horizontally in a longitudinal direction, a front side link connected rotatably at a lower end portion thereof to a front end portion of the lower side link and which is tilted forward, a rear side link connected rotatably at a lower end portion thereof to a rear end portion of the lower side link and which is tilted forward, an upper side link connected rotatably at a front end portion thereof to an upper end portion of the front side link and connected rotatably at a rear end portion thereof to an intermediate portion of the rear side link, and a load supporting link with a rear end side thereof placed slidably on the upper end portion of the rear side link and a front end side thereof connected rotatably to a front end portion of the upper side link, a biasing element which biases the upper side link and the load supporting link so as to push the same upwards, and a regulating element which regulates tilting of the rear side link rearwards, wherein a link length of the front side link is longer than a link length of the rear side link, wherein in the state where the head of a person is not placed on the head placement member, a product of a sine of a tilt angle towards the front and the link length of the front side link is twice or larger than that of the rear side link, the tilt angle towards the front of the rear side link exceeds 0 degree and is equal to or smaller than 20 degrees, and the load supporting link is positioned at a most elevated position by being biased from the biasing element and by being supported by the upper end portion of the rear side link, and the biasing force of the biasing element is set so that the load supporting link descends to a most descended position when the front side link and the rear side link falls forward in the state where the head of a person is placed on the head placement member.
 2. The pillow according to claim 1, wherein in the state where the head of a person is not placed on the head placement member, upper surfaces of the load supporting link and the head placement member are tilted upwards toward the front.
 3. The pillow according to claim 1, wherein the biasing element is a tension spring with one end side being fixed to a portion of the load supporting link extended forward from a rotatable connecting portion with the front side link, and other end side being fixed to a vicinity of the rear end portion of the lower side link.
 4. The pillow according to claim 1, wherein the pillow is configured so as to make an impact absorbing member positioned between the lower side link and each of the front side link and the rear side link, respectively, when the front side link and the rear side link fall forward. 